1. Field of the Invention
The present invention relates generally to an apparatus for manufacturing readily soluble granular substances such as milk, coffee, seasoning and like products from powdered materials, and more particularly to an apparatus for manufacturing granules of uniform grain sizes with improved efficiency. The invention has two vertical outer and inner cylindrical bodies of different length and diameter arranged concentrically and spaced from each other for allowing quantities of powdered material to fall by gravity from a distributor through the space in the outer cylindrical body and through the circumferential gap between the two bodies in a thin, ring-like continuous curtain form. Pneumatic means on the outer cylindrical body produces a whirling stream of compressed air in the gap, and a first means on the closed top of the inner cylindrical body introduces a stream of steam into the inner body and blowing steam against the curtain-form powdered material from the inside. A second means at the open bottom of the outer body blows steam against the curtain-form material from the outside.
2. Description of the Prior Art
There are already known a number of apparatues for forming powdered materials into granules or granular substances under a humidified atmosphere, and those apparatuses employ a vibratory screening device or a pneumatic system as a distributor of the powdered materials. Distributing the powdered material by means of the vibratory screening device may disadvantageously cause the screening device to become clogged with the material if the material has a strong cohesive force between its particles. Furthermore, it is very likely that the material is distributed in gross or agglomerated sizes through the screening device, which makes it difficult to humidify those sizes of powders uniformly. An other disadvantage of the screening device is that the end products contain an increased amount of relatively fine granules. The pneumatic distribution system is disadvantageous in that a relatively long tubular passage is required to distribute quantities of powdered material in a uniform manner and yet it is difficult to obtain the uniform distribution of the material inside the tubular passage. A further disadvantage is that particles of the powder travel with great velocity through the passage, thereby lowering the efficiency of humidifying it and thus increasing the rate of production of the relatively fine granules.